APA Publications, [date of publication not identified]
Buku Referensi
Tuttle, 2011
Buku Referensi
World Express Mapping Sdn. Bhd, [date of publication not identified]
Buku Referensi
World Express Mapping Sdn. Bhd, [date of publication not identified]
Buku Referensi
Indonesia Scholars Journal, 2016
Majalah, Jurnal, Buletin